
abstract class GirlFriend { 
     abstract void speak(); 
     abstract void cooking(); 
  } 
  class ChinaGirlFriend extends GirlFriend { 
     void speak(){ 
        System.out.println("你好"); 
     } 
     void cooking(){ 
        System.out.println("水煮鱼");  
     } 
  } 
  class AmericanGirlFriend extends GirlFriend { 
     void speak(){ 
        System.out.println("hello"); 
     } 
     void cooking(){ 
        System.out.println("roast beef");  
     } 
  } 
  class Boy { 
     GirlFriend friend; 
     void setGirlfriend(GirlFriend f){ 
         friend = f; 
     } 
     void showGirlFriend() { 
        friend.speak(); 
        friend.cooking(); 
     } 
  } 
 


 

